1. Field of the Invention
The invention relates to the continuous production of composite panels comprising a foam core made of an expanded resin and facings particularly resulting in a strong, homogeneous panel.
2. Background of the Prior Art
Composite panels of the type addressed herein are conventionally obtained, for example, by casting of a mixture containing a heat-expandable resin on a lower facing passing continuously, then by superposition of an upper facing on the cast layer while it is expanding, followed by a calibration after expansion of the composite, and cutting of the panels into the desired lengths after complete hardening of this composite.
This process is not entirely satisfactory. Because of an imperfect distribution of the resin during casting of the mixture, a casting that is generally performed by a casting head driven in a back and forth movement crosswide to the direction of advance of the lower facing acting as a support, or again by a stationary head placed perpendicular to the direction of displacement, varying thicknesses occurs in the formed layer. These irregularities are amplified by expansion of the resin and can be eliminated or at least attenuated only by a calibration considerably reducing the thickness of the composite. Since it is not possible to maintain the integrity of the panel in the lateral direction in the calibration zone for reasons indicated below, this calibration, even in the case of slight reductions of the thickness, for example, on the order of a few millimeters, particularly causes lateral creep of the upper part of the cast layer which, in the case of a production process using heating from below, is softer than the lower part. This creep then causes a rupture line or surface and thereby a weakening of the mechanical properties of the panels produced. When the composite is held laterally in the calibration zone, the excess material flows back upstream, accumulates in front of the calibration passages and disturbs production.
This invention eliminates the noted drawbacks. The process according to the invention makes it possible to obtain panels exhibiting a good geometric definition and good mechanical properties.